Assumptions of herd immunity to the coronavirus as more people get infected may be wrong, and patients who have suffered one bout of the virus could face reinfection, according to a new study by British researchers that found that people who recover from COVID-19 tend to lose their immunity within several months.
The Guardian reported on Sunday that a team from King’s College in London found that the amount of antibodies in recovered patients’ blood was significantly down after three months, meaning they could be vulnerable to reinfection.
The study examined 90 patients and healthcare workers at Guy’s and St Thomas’ NHS foundation trust and found that while 60 percent of those in the study had a “potent” antibody response when infected with the virus, that level of effectiveness was only maintained in 17% of people three months later.
According to the report, in some cases antibody levels were no longer detectable.
For some viral diseases such a measles, overcoming the sickness confers immunity for life.
But for RNA-based viruses such as Sars-Cov-2 — the scientific name for the virus that causes the COVID-19 disease — it takes about three weeks to build up a sufficient quantity of antibodies, and even then they may provide protection for a limited period.
That means people could catch the virus year after year, like the common cold.
If confirmed by more research, it would mean that hopes for getting rid of the virus now depend chiefly on the development of an effective and safe vaccine, perhaps with boosters.
“People are producing a reasonable antibody response to the virus, but it’s waning over a short period of time and depending on how high your peak is, that determines how long the antibodies are staying around,” Dr. Katie Doores, lead author on the study, told the Guardian.
“Infection tends to give you the best-case scenario for an antibody response, so if your infection is giving you antibody levels that wane in two to three months, the vaccine will potentially do the same thing,” Doores said. “People may need boosting and one shot might not be sufficient.”
Serology tests on the blood can show antibodies indicating whether someone has had the virus in the past and may have some level of immunity.
Some governments are pushing antibody tests as a way to examine levels of potential herd immunity as they try to restart economies after virus lockdowns.
Prof. Jonathan Heeney, a virologist at the University of Cambridge, said the study was another example of evidence that immunity to the coronavirus may not be permanent.
“Most importantly, it puts another nail in the coffin of the dangerous concept of herd immunity,” he told the Guardian.
“I cannot underscore how important it is that the public understands that getting infected by this virus is not a good thing. Some of the public, especially the youth, have become somewhat cavalier about getting infected, thinking that they would contribute to herd immunity. Not only will they place themselves at risk, and others, by getting infected, and losing immunity, they may even put themselves at greater risk of more severe lung disease if they get infected again in the years to come,” he said.
Prof. Arne Akbar, an immunologist at University College London, told the daily that antibodies are not the only factor being examined, with some evidence that T cells produced by the body to fight colds may also protect people.
However, the World Health Organization has also warned there is still no evidence that people who test positive were immunized against getting infected again.
“There is certainly some evidence with regard to T cells, that if you have a previous coronavirus infection you may be able to mount a more rapid response to COVID-19,” said the WHO’s Michael Ryan at a press conference in May.
“But there’s no empirical evidence that previous coronavirus infections protect you from infection with COVID-19. The jury is still very much out on that,” he added.
Agencies contributed to this report.